1. Field of the Invention
The present invention relates to a technique for decomposing organic contaminants contained in crop land soil, underground water, or the like. In particular, the present invention relates to a technique for decomposing contaminants from soil, underground water, or the like, which has been contaminated by a plurality of organic contaminants, or to a technique for decomposing a persistent organic contaminant, by utilizing soil bacteria.
2. Description of the Related Art
In recent years, a bio-remediation technique, which is able to decontaminate contaminated soil or the like and make it safe by means of the natural degrading abilities of microorganisms such as bacteria, has attracted attention as a technique for decomposing persistent organic contaminants or POPs in low concentration distributed widely in crop land soil, or the like. However, in the conventional bio-remediation technique, even though someone wants to utilize microorganisms such as bacteria for decontamination effectively, the discovery of degrading bacteria that decompose an organic contaminant effectively has been difficult. Alternatively, even if the degrading bacteria can be discovered, the bacteria have its own living environment and the density of the degrading bacteria can be low in its natural state, so a contaminant cannot be effectively removed from the environment. In particular, in consideration of the application of the bio-remediation technique to contaminated soil or the like, problems have risen such that the degrading bacteria die as a result of effects of the physical and chemical properties of contaminated soil or predation by protozoa in the contaminated soil. Therefore, even though there are increasing demands for an effective bio-remediation technique, in actuality, such a technique has not yet spread widely.
On the other hand, the inventors of the present invention have found that a porous material having a predetermined absorption constant or specific surface can be utilized as a degrading bacterial habitat for organic contaminants and have developed technique for enriching and isolating a specific degrading bacterial species (Japanese Patent No. 3030370: Patent Document 1, Japanese Patent No. 2904432: Patent Document 2, and WO 00/078923: Patent Document 3). Those technologies have allowed any kind of organic contaminant which has been used in an agricultural chemical or the like and remained in environments, for example in soil, to be decomposed and removed by thickly enriching and purifying degrading bacteria capable of decomposing the organic contaminant.
In many cases, two or more organic contaminants may cause environmental contamination such as soil and water contamination. However, there is no in situ technique developed for simultaneously decomposing those contaminants.
In addition, it is difficult to decompose organic contaminants, such as organochlorine pesticide PCNB (quintozene: pentachloronitrobenzene), which is hardly decomposed, and simazine (2-chloro-4,6-bis (ethylamino)-1,3,5-triazine), which has a long half-life and a low soil-adsorption coefficient. Therefore, novel technique for more effectively decomposing the organic contaminants has been demanded in the art.